Laser Interference-based Surface Treatments of Carbon ... · Laser Interference-based Surface Treatments of Carbon Fiber Polymer Composites and ... (adhesive bonding, ... adhesive

Managed by UT-Battelle for the Department of Energy

Laser Interference-based Surface Treatments of Carbon Fiber Polymer Composites and

Aluminum for Enhanced Bonding

Adrian S. Sabau Oak Ridge National Laboratory

Oak Ridge, TN 37831

Global Automotive Lightweight Materials Detroit, MI

August 23-25, 2016


Collaborators •  Claus Daniel (optical setup, facility installation, laser-interference)

•  C. David Warren (adhesive bonding, laser ablation of carbon fiber polymer composites),

•  Jian Chen (optical setup),

•  Don Ermand (LabView, Mechanical testing),

•  John Henry (profillometry),

•  Harry Meyer III (XPS – surface chemistry),

•  Clayton M. Greer; Alexandra Hackett, Curtis Frederick (Optical micrographs, 3-12 months assignments UT-Knoxville).

Tim Skszek (Cosma Eng.), Mary M. Caruso (3M), and James Staagaard (Plasan)


Vehicles Are Multi-Materials Assemblies

Successful Al-CF joining will enable an increase in multi-material use in automotive and consequently lead to significant weight reduction.

Multi-Material Systems •  Future vehicles will increase the use of mixed material systems to deliver

lightweighting solutions needed to maximize vehicle performance and efficiency (p. 6, Materials Technical Team Roadmap)

Lightweighting, Joining and Assembly. •  High-volume, high-yield joining technologies for lightweight and

dissimilar materials needs further improvement. 2.5-3* •  Joining methods must be rapid, affordable, repeatable, and reliable and

must provide at least the level of safety that currently exists in production automobiles. 2.5-4*

* VT Program, Multi-Year Program Plan 2011-2015, Dec 2010, pp. 1.0-2, 2.5-3, 2.5-4.


High-Volume, High-Yield Technologies Are Needed for Joining Dissimilar Materials

Current surface preparation for adhesive joining technologies are:

•  Labor intensive •  Operator dependent:

Surface preparation via grit blasting or sanding

•  Low-volume •  Ecological expensive

(Solvent Cleaning)

http://www.nytimes.com/2016/08/12/automobiles/the-superglue-diet-how-to-make-a-lighter-fuel-sipping-car.html?emc=eta1


Lasers offer a possibility for adhesive joining: mature technology for surface cleaning and

surface preparation

http://www.lasercleanall.com/


Traditional one-laser-beam rastering induces structures limited to the beam size

Method Traditional laser

Structure 1 dimple per spot, or 1 feature per line

Sizes 0.5-2 mm diameter, 10 micron depth

Large beam size: •  High-productivity, •  Low-concentration of

laser-induced structures

Small beam size: •  Low-productivity, •  High-concentration of

laser-induced structures


Interference technique Interference of multiple wave yields alternating high & low energy variation on subscale beam size: •  Constructive interference of intensifies power, •  Destructive interference minimizes power,

Beam 1 Beam 2

)2/sin(2 αλ

=d

Schematic from Ekinci (SPIE) 10.1117/2.1201306.004958

•  Light in both beams must be temporally and spatially coherent in the region where interference fringes are to be obtained.

•  Polarization properties of the two beams must be compatible.

•  The irradiances of the two beams must be close in magnitude.


Paradigm shift: more structuring at the same productivity

Method Traditional laser Laser-interference

Structure 1 dimple per spot 200-20,000 pits (wells) per spot

Sizes 500µm dia, 10 µm depth 1µm dia, <500 nm depth

Features of the structured surface morphology: •  Undulation spacing: 0.5 – 50 µm, •  Density: 200-20,000/cm, •  Feature size: 1- 500nm, •  Structured area: 0.27cm2/shot, •  Velocity: 10,000 lines at a time, 79 million

dots at a time, up to 162 cm2/min.


Laser interference patterns for polished steel

Actual setup 10 µm

10 µm

Unprocessed

Laser processed

Vertical lines indicate “ridges and valleys” produced by the two-beam laser-interference


Actual setup of the laser-interference processing

Laser spot. Beam 1

Beam 2

Sample mounted on a translational stage controlled by LabView.

•  Q-switched Nd:YAG laser system with an harmonic generator enabling the selection of one very sharp wavelengths of 1064, 532, 355, or 266nm.

•  Pulse duration 10ns (heating and cooling rates above 1012K/s, frequency = 10Hz)


What is laser interference good for?


Pin-on-disk tribometer tests showed an increase in the oil film lifetime of 14X compared

to that of an unpatterned reference

Duarte et al. (2008) Adv. Eng. Mater., 10: 554–558. doi: 10.1002/adem.200700321


Pin-on-disk tribometer tests showed an increase in the oil film lifetime of 130X

compared to that of an unpatterned reference

Duarte et al. (2008). Adv. Eng. Mater., 10: 554–558. doi: 10.1002/adem.200700321


Typical surface profiles obtained with laser-interference for lubrication applications

C. Gachot, et al., Dry friction between laser-patterned surfaces: …, Tribol. Lett. 49, 193-202 (2013).


Friction coefficient was decreased by using laser-interference structured surfaces by

4.7X (lubricated) and 2X (dry friction)

C. Gachot, et al., Dry friction between laser-patterned surfaces: …, Tribol. Lett. 49, 193-202 (2013).

Ball-on-disk sliding tests


Laser interference as a surface treatment for joining


Surface preparation procedures

Joint Type Preparation of CFPC Preparation of Al Open time Joining

Baseline

• Abraded using Scotch-BriteTM,

• Ultrasonically cleaned using ethanol for 5 min.

• Abraded using Scotch-BriteTM,

• Ultrasonically cleaned using ethanol for 5 min.

None Bonding right after preparation

Laser structuring

• Laser-interference structuring

• Stored in plastic cases

• Laser-interference structuring

• Stored in plastic cases

3-14 days (in plastic

cases)

*air-off with compressed air prior to bonding

*Prior to joining, the laser-structured samples were air-off with compressed air: (a)  No ethanol cleaning (b)  No removal of the

oxide layer on the Al surface.


The use of a fixture ensured consistency of the joining process

The joint geometry (overlap of 1x1 in., i.e., 25.4x25.4 mm) was controlled by appropriate fixturing (ASTM D5868): •  glass beads were used to ensure an

adhesive bondline thickness of 0.01 in (0.25 mm).

•  a fixturing pressure was allowed.

3M provided 3 different adhesives: Urethane, Acrylic and Epoxy.


All baseline joints failed by fracture of the adhesive layer (cohesion failure)

Clean fracture surfaces indicate poor adhesive adherence

Baseline joints were prepared without “open time” Al and composite specimens were prepared without involving laser structuring: •  abraded using Scotch-BriteTM, and •  ultrasonically cleaned using ethanol.

!


Laser-interference structuring was conducted on as-received specimens,

without any additional surface preparation

Actual setup

CFPC: mold release, rolling marks, contaminants

Al: rolling channels, microcracks, lubricant film


Bonded as-received

Flat adhesive-resin interface

6 shots per spot

adhesive in direct contact with CF

Bonded after ablation

After laser-ablation, the adhesive-composite interface is non-planar and fiber reinforced

8 shots per spot Damaged CF


2 shots per spot

Undamaged CF



For 6mm laser spot size, the quality of carbon fiber structuring increases with number of pulses per spot

Pulse fluence 1.24 J/cm2!

2 pulses per spot

4 pulses per spot

8 pulses per spot


For 6mm laser spot, the melting area reduce with decreasing number of pulses

Pulse fluence 1.17 J/cm2!

12 pulses per spot

Surface melting indicated by: drop-like network pattern

8 pulses per spot

web-like network structure (melting)

network patterning at a finer length-scale than LHS and RHS (more structuring, less melting)

6 pulses per spot

Structuring areas increase


(a)

As-received, unprocessed.

Ra=226nm

The surface roughness increased from 226 nm for the as-received surface to 392 nm for

the laser-interference structuring surface

Condition Ra [µm]

Rq [µm]

Rt [µm]

untreated 0.226 0.286 3.21

Laser treated 0.391 0.493 4.68

Optical surface profile 10 pulses/spot

(b) Ra=392nm

Rt

λ=355 nm, pulse fluence 1.2 J/cm2


Laser-Structured Joints are more Ductile, Indicating an Enhanced Bonding of Adhesive to Both Al and CFPC

After testing

Displacement @ maximum load is a direct measure of the energy absorbed by the joint during the shear-lap test.

Laser structured joints can absorb approx. 2.5X more energy than baseline joints. The energy absorbed during the tensile test was 26.3 and 66.8 Joules for the baseline joint and laser-structured joint, respectively.

!

Data obtained for adhesive DP810 provided by 3M.


X-ray photoelectron spectroscopy was used to investigate the Ar-ion depth profile for Al specimens in the as-received

and laser-structured conditions

Com

posi

tion

(at%

) C

ompo

sitio

n (a

t%)

0

20

40

60

80

0 50 100 150 200 250 300 350

Al(M) Al(O) C(C-C) C(carb.) O Mg

0

0.5

1

1.5

2

0 50 100 150 200 250 300 350

Na Cl Zn S

As received

Distance from top surface [nm]


Laser-interference is very effective in cleaning the surface, eliminating the need for solvent cleaning

0 0.1 0.2 0.3 0.4 0.5 0.6

0 50 100 150 200 250 300 350

Cu Na Cl

After 5 shots/spot

Com

posi

tion

(at%

)


After 2 shots/spot

0 0.1 0.2 0.3 0.4 0.5 0.6

0 50 100 150 200 250 300 350

Cu Na

Cl Zn

Com

posi

tion

(at%

)



Shear-lap strength for laser-interference structured – by rastering and spot by spot for all adhesives

620

460 810

Adhesive! % increase by raster!

810! 12.7-14.8!460! 12.8!620! 35.3!

Adhesive!% increase

Spot-by-spot!

810! 16.3!460! 8.2-12.8!620! 25.4!


Baseline joints: 620 adhesive

Baseline joints: 460 adhesive

Clean fracture surfaces indicate poor adhesive adherence

Baseline = No laser structuring

Adhesive – Al Interface Failure

Laser-structured joints: 620 adhesive

Laser-structured joints: 460 - adhesive

Both surfaces have residual adhesive

Failure in the composite

Laser structured joints

Top Ply of Composite Delaminated

Failure mode changed due to laser-structuring


Evaluated Double Lap Shear for Laser-interference structured samples, [0.25 mm, 6mm beam, 810 Adhesive]

Laser-structured samples showed a significant increase in ductility.

50% of the samples failed in the bulk of the aluminum away from the joint.

Data obtained with •  0.25 mm bondline, •  6mm beam size, •  810 adhesive.


Corrosion Test ASTM B117 was performed by Cosma

0

500

1000

1500

2000

2500

0.25mm Baseline

0.25mm Ablation

0.85mm Baseline

0.85mm Ablation Sh

ear L

ap S

tren

gth

(PSI

)

Specimen Preparation

No Corrosion With Corrosion

•  Bondline thickness had a minimal effect on SLS of laser-interference samples. •  Shear lap strength of thin bondline samples degraded the most. •  For laser-interference samples, the thick bondline provided superior corrosion

resistance.


1.  Sabau A.S., Greer C.M., Chen J., Warren C.D., and Daniel C., Surface Characterization of Carbon Fiber Polymer Composites and Aluminum Alloys after Laser Interference Structuring, JOM, Vol. 68, pp. 1882-1889, 2016.

2.  Sabau A.S., Chen J., Warren C.D., Erdman D.L. III, Daniel C., Skszek T., and Caruso Dailey M., A Laser Interference-Based Surface Treatment of Al and Carbon Fiber Polymer Composites for Enhanced Bonding, paper LB15-0070, SAMPE Conference and Exhibition, Long Beach, CA, May 23-26, 2016.

3.  (invited) Sabau, A. S., Chen, J., Jones, J. F., Hackett, A., Jellison, G. D., Daniel, C., Warren, D. and Rehkopf, J. D. (2015) Surface Modification of Carbon Fiber Polymer Composites after Laser Structuring, in Advanced Composites for Aerospace, Marine, and Land Applications II (eds T. Sano and T. S. Srivatsan), John Wiley & Sons, Inc., Hoboken, NJ, USA. doi: 10.1002/9781119093213.ch23

4.  J. Chen, A.S. Sabau, J. F. Jones, A. Hackett, G. D. Jellison, C. Daniel, and D. Warren, "Aluminum Surface Texturing by Means of Laser Interference Metallurgy," 2015 TMS Annual Meeting & Exhibition, Proceedings: Light Metals 2015: Aluminium Processing, pp. 427-429, Orlando, FL.

5.  A.S.Sabau, C.D. Warren, C. Daniel, J. Chen, D.L. III Erdman, Laser Nanostructured Surface Preparation for Joining Dissimilar Materials, Patent application No.: 62/132,296, UTB Ref. No.: 3405.0, Filed date March 12, 2015.

Publications


Technical Summary - Laser-structured joints are more ductile, indicating an enhanced bonding of adhesive to both Al and CFPC

•  Laser-interference process can effectively: –  ablate the resin (on top surface of CFPC) without excessive CF

damage, –  Structure the Al surface, increasing its roughness,

•  Failure mode changed due to laser-structuring changed to “failure in the composite” from the “cohesive failure in the adhesive” for baseline joints.

•  Shear lap strength, maximum load, and displacement @ max. load for joints made with laser-interference structured surfaces were increased by approximately 14.8%, 16%, and 100%, respectively over those measured for the baseline joints.

•  Joints made with laser-structured surfaces can absorb approximately 150% more energy than the baseline joints.

•  For laser-interference samples, the thick bondline provided superior corrosion resistance.

All results obtained without empirical, labor-intensive surface preparation methods that are incompatible with automation.


Objective met: Develop a Breakthrough Joining Technology for Joining Carbon Fiber Polymer Composites (CFPC) and

Aluminum (Al) Components

http://www.extremetech.com/extreme/162582-bmw-i3-will-bmws-new-ev-finally-be-the-breakthrough-for-carbon-fiber-cars

Goals of laser-structured CFPC and Al: •  Elimination of empirical, labor-intensive

surface preparation (sanding and inherent process variability)

•  Eliminates solvent cleaning by removal of mold releases and surface contaminates

•  Provides a larger, non-planar contact area – by sub-scale beam size laser-interference structuring

•  Yields a fiber reinforced adhesive/composite interface by removing the resin rich surface layer

•  Increases Joint ductility by 2X (Crash Energy Absorbance)

CF

Al AHSS

CF

CF


Speed and Cost “To use or not to use (direct laser interference

patterning), that is the question” - Lasagni et al. (2015)

*Lasagni et al. (2015) one operator working 52 weeks, 39 hours a day with 100% overhead, equipment cost distributed in 3 years at maximum achievable fabrication speed. (Source: Proc. SPIE 9351, Laser-based Micro- and Nanoprocessing IX, 935115 (March 12, 2015); doi:10.1117/12.2081976).

1-st Lab setup 2-nd Generation Roll-to-roll processing

Achieved Max. fabrication speed

0.1 m2/min (metals) (25 W IR system)

0.70 m2/min (PC-polymer) (180 W IR-system)

0.17 m2/min (TCO) (6 W UV system)

Estimated max. fabrication speed

2-5 m2/min (metals) (>600 W IR system)

1-2 m2/min (TCO) (50 W UV system)

*Estimated fabrication cost

1.31 €/m2 3.08 €/m2


Acknowledgments

Actual setup

This research was conducted at UT-Battelle, LLC, under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy for the project “Laser-Assisted Joining Process for Aluminum and Carbon Fiber Components” and has been funded by the Office of Energy Efficiency and Renewable Energy, Vehicle Technologies Office, Lightweight Materials Program.

Method Number of structures per spot Size of structures

Traditional laser 1 dimple (or 1 line) 0.5 to 1mm = spot size

Laser-interference 200-20,000 pits (wells) (or lines) 1µm dia, <500 nm depth

Laser spot Dots for

3 laser beams

Lines for 2 laser beams

Documents

Laser Interference-based Surface Treatments of Carbon ... · Laser Interference-based Surface Treatments of Carbon Fiber Polymer Composites and ... (adhesive bonding, ... adhesive